[Dev] Check list of requirements for blocks

[John Anderson]

As the apps group spends more time designing CPIA blocks, we've found it 
useful to come up with a short check list of block features that needs 
to be addressed during the design phase. I thought this list might be of 
interest to a broader group of people, so I'm emailing it to the dev list

When designing a CPIA block we need to address:

- The data (attributes) that the block needs to persist
- Each block should usually implement SynchronizeFramework to make the 
model (wxWidgets counterpart) match the data stored in the block
- A list of Chandler Events that the block handles
- A list of Chandler Events that the block generates
- The wxWidgets counterpart should implement del to remove itself from 
the global association dictionary
- A list of the wxWidgets events that the wxWidgets counterpart should 
respond to
- If the block has a content spec, the form takes
- If any functionality can't be expressed in data driven way, could it 
be done using some other mechanism, e.g. delegation, which would make it 
more friendly to a direct manipulation U/I builder.

John